diff options
| author | David Sterba <dsterba@suse.com> | 2024-02-20 10:25:29 +0100 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2024-02-20 10:26:09 +0100 |
| commit | 93cdc1c2fc8df31a7943d2199282893eece4df53 (patch) | |
| tree | 5b94f662cbdb62acbb2cbcceee1c94d2b51bf5af | |
| parent | d03594b0313db71413b9dcb040f8d5c4da7213b1 (diff) | |
| download | btrfs-progs-93cdc1c2fc8df31a7943d2199282893eece4df53.tar.gz | |
btrfs-progs: docs: clarify inode numbers
Update wording and add an example.
[ci skip]
Issue: #729
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | Documentation/ch-subvolume-intro.rst | 29 |
1 files changed, 22 insertions, 7 deletions
diff --git a/Documentation/ch-subvolume-intro.rst b/Documentation/ch-subvolume-intro.rst index 9ca39d0a..20a46334 100644 --- a/Documentation/ch-subvolume-intro.rst +++ b/Documentation/ch-subvolume-intro.rst @@ -1,7 +1,8 @@ A BTRFS subvolume is a part of filesystem with its own independent file/directory hierarchy and inode number namespace. Subvolumes can share file extents. A snapshot is also subvolume, but with a given initial content of the -original subvolume. A subvolume has always inode number 256. +original subvolume. A subvolume has always inode number 256 (see more in +:docref:`Inode numbers <Subvolumes:subvolume-inode-numbers>`). .. note:: A subvolume in BTRFS is not like an LVM logical volume, which is block-level @@ -15,8 +16,8 @@ changed. A subvolume in BTRFS can be accessed in two ways: -* like any other directory that is accessible to the user -* like a separately mounted filesystem (options *subvol* or *subvolid*) +- like any other directory that is accessible to the user +- like a separately mounted filesystem (options *subvol* or *subvolid*) In the latter case the parent directory is not visible and accessible. This is similar to a bind mount, and in fact the subvolume mount does exactly that. @@ -143,13 +144,27 @@ the 4th column: 27 21 0:19 /subv1 /mnt rw,relatime - btrfs /dev/sda rw,space_cache ^^^^^^ +.. duplabel:: subvolume-inode-numbers + Inode numbers ------------- -A proper subvolume has always inode number 256. If a subvolume is nested and -then a snapshot is taken, then the cloned directory entry representing the -subvolume becomes empty and the inode has number 2. All other files and -directories in the target snapshot preserve their original inode numbers. +A directory representing a subvolume has always inode number 256 (sometimes +also called a root of the subvolume): + +.. code-block:: none + + $ ls -lis + total 0 + 389111 0 drwxr-xr-x 1 user users 0 Jan 20 12:13 dir + 389110 0 -rw-r--r-- 1 user users 0 Jan 20 12:13 file + 256 0 drwxr-xr-x 1 user users 0 Jan 20 12:13 snap1 + 256 0 drwxr-xr-x 1 user users 0 Jan 20 12:13 subv1 + +If a subvolume is nested and then a snapshot is taken, then the cloned +directory entry representing the subvolume becomes empty and the inode has +number 2. All other files and directories in the target snapshot preserve their +original inode numbers. .. note:: Inode number is not a filesystem-wide unique identifier, some applications |